Fire extinguisher systems that use a liquefied extinguishant gas to disseminate a fire suppressing powder offer substantial advantages over traditional technologies. The simultaneous application of two modes of fire suppression produces a synergy that results in a substantial improvement in efficacy over single-phase systems. As a result, the area coverage provided by a mixed phase extinguisher is significantly greater than that provided by a single-phase extinguisher of the same size.
The development of a fire extinguisher system which uses an extinguishant liquefied gas and a fire suppressing powder presents a number of technical challenges. These include the development of a formulation which is not subject to packing or clogging, which is compliance with US EPA requirements regarding ozone depleting substances, and which has the general physical design of a compact conventional extinguisher.
Mixed agent fire suppression systems which combine two modes of fire suppression in a single system can achieve a greater efficiency than conventional systems. First developed in the early 1980's, these fire extinguishers typically contain a blend of a chlorofluorocarbon (Halon) based fire suppressant gas/liquid and a monoammonium phosphate (MAP) based powder along with a vinyl gelling agent (Carbopol). Halons such as Halon 1301 (trifluorochoromethane) and Halon 1211 (difluorochlorobromomethane) have been employed for this purpose. These agents were combined to form a stable, highly efficient fire-fighting gel. Because the fire suppression mechanism of each individual agent compliments the other, a smaller quantity of the blended agent is required than would be needed for either single agent system. An example of the composition that could be employed for this purpose is set forth in U.S. Pat. No. 4,652,383, which is incorporated herein by reference.
Since the units are pre-engineered and self-contained, they can provide fire protection in areas where it is not practical to run a network of piping. Installation of a network of piping to facilitate fire protection is extremely costly and some cases not functionally possible.
The mixed phase systems provide much easier clean up than many other fire suppression products. Aqueous-based fire suppression units, such a water sprinkler systems, result in severe water damage to the protected area. 70% or more of the costs of insurance claims are attributable to water damage following a fire suppression event. The dry powder residue formed in the suppression of fires employing the mixed phase system of the present invention is easily vacuumed, making the system an attractive alternative for applications in which water or chemical damage is an issue.
In 1988, the Montreal Treaty phased out the production of chlorobromofluorocarbons and chlorofluorocarbons, including the Halon agents used in the mixed-phase extinguisher systems. These compounds were found to promote damage to the ozone layer of the atmosphere and thus threaten human health by increasing exposure to ultraviolet radiation.
Over the past several years, certain ozone safe alternatives to Halon have been developed. These new compounds differ from those they replace in a number of fundamental ways. The formation of a stable, free-flowing suspension depended on the specific molecular interaction of the powder, liquid, and the gelling agents. It was found that simply replacing the Halon in the original formula with one of the new compounds would not necessarily work. Furthermore, changes in the physical properties of the extinguishant-liquefied gas had a significant adverse effect on the discharge properties of the extinguisher device.
Therefore, a new mixed phase fire suppression agent composition for delivering same needed to be developed using only Underwriters Laboratory (“UL”) acceptable components. Furthermore, the current UL specifications required for compliance are far more stringent. Thus, it is necessary to deploy an extinguisher system that meets the appropriate UL specifications. It has been determined that every element of a formula composition and extinguisher design is critical to the development of a unit which meets the rigorous requirements of the UL specifications. An extinguisher employing a mixed phase agent must be subjected to fire tests as per the Underwriters Laboratories specification 1254 for dry chemical extinguishers. Fire tests are performed in order to assure and certify the performance characteristics of these extinguisher systems.
Mixed-phase fire suppression technology provides substantive advantages over conventional systems. If they were available, extinguishers which are EPA compliant could make possible a variety of practical fire suppression applications.